a. Field of the Invention
This invention relates to a rotary power slip assembly which is removably mountable with a rotary drilling table. It is particularly useful for running drill pipe in and out of a well bore and for running casing pipe into a well bore. The tool of this invention permits the use of the power drive assembly associated with the rotary table to be used in the aforesaid running operations.
B. Description of the Prior Art
One tool has heretofore been offered to the trade which utilizes slips mounted in a rotary housing, but such slips are operated by an air actuated cylinder mounted in a stationary portion of the rotary table. Accordingly, there is a mechanical linkage in the form of a shifting ring. However, tools of the aforesaid type are not fully satisfactory in all instances. For example, the aforesaid shift ring is subject to fouling and malfunctioning. It is also desirable to have a power slip assembly wherein the slips are not exposed above the surface of the drill table to any large extent and wherein the slips are removable so that the master bushing of the rotary drilling table can be converted to API specifications readily. It is also desirable to have a power slip assembly which is readily movable from the drilling table so that other drilling operations may be carried on.